Re: [Xen-devel] [PATCH v7 12/19] x86/VPMU: Initialize PMU for PV guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.06.14 at 19:40, <boris.ostrovsky@xxxxxxxxxx> wrote:
> Code for initializing/tearing down PMU for PV guests
> ...
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4031,7 +4031,8 @@ static hvm_hypercall_t *const 
> pvh_hypercall64_table[NR_hypercalls] = {
>      [ __HYPERVISOR_physdev_op ]      = (hvm_hypercall_t *)hvm_physdev_op,
>      HYPERCALL(hvm_op),
>      HYPERCALL(sysctl),
> -    HYPERCALL(domctl)
> +    HYPERCALL(domctl),
> +    HYPERCALL(xenpmu_op)

How is this change related to the subject and description?

> +static int pvpmu_init(struct domain *d, xen_pmu_params_t *params)
> +{
> +    struct vcpu *v;
> +    struct page_info *page;
> +    uint64_t gfn = params->d.val;
> +
> +    if ( !params || params->vcpu >= d->max_vcpus )
> +        return -EINVAL;
> +
> +    page = get_page_from_gfn(d, gfn, NULL, P2M_ALLOC);
> +    if ( !page )
> +        return -EINVAL;
> +
> +    if ( !get_page_type(page, PGT_writable_page) )
> +    {
> +        put_page(page);
> +        return -EINVAL;
> +    }
> +
> +    v = d->vcpu[params->vcpu];

I'm sure I asked this before - what guarantees (now as well as
going forward) that you get non-NULL here? Various existing
code paths properly verify both d->vcpu and d->vcpu[...] not
being NULL, so you should do this consistently too.

Jan


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